how to uses str2sym

clear all;clc

disp('------');

disp('The Nonlinear systems should be written in thefollowing form');

disp('Sliding Mode Controller for a class of Nonlinear systems');

disp(' State space equations x=f(x)+gu ');

disp('-----------');

n=input('Number of states:=');

nin=input('Number of inputs:=');

x=sym(zeros(1,n));

u=sym(zeros(1,nin));

par=input('Parameters ','s');

eval(sprintf('syms %s',par));

parameters=sprintf('%s',par);

for j=1:n

eval(sprintf('syms x%d',j))

x(:,j)=sprintf('x%d',j);

end

for k=1:nin

eval(sprintf('syms u%d',k));

u(:,k)=sprintf('u%d',k);

end

syms u

f=input('The vector f(x):=','s');

g=input('The vector g(x):=','s');

Hc=input('The output variables:=','s');

[Lhf,Lhg,dh,L,u,r]=NonContSidFed(f,g,Hc,x,u);

[Surf,dSurf,dd,K,Uc]=SlidingModeTerms(Hc,L,r,Lhg);

Answer 1

[Pranav Verma]

Hi Rim,

The str2sym function takes in a symbolic expression in a string form as input & evaluates it. Please refer to the below example illustrating the same:

>> st = '2+2';
>> str2sym(st)
 
ans =
 
4

Thanks